diff --git a/spec/integration/request_spec.rb b/spec/integration/request_spec.rb
index 99bfefa..26919f1 100644
--- a/spec/integration/request_spec.rb
+++ b/spec/integration/request_spec.rb
@@ -1,4 +1,5 @@
 require_relative '_lib'
+require 'webrick'
 
 describe RestClient::Request do
   before(:all) do
@@ -124,4 +125,62 @@ describe RestClient::Request do
     end
   end
 
+  class HostEchoServer < WEBrick::HTTPServlet::AbstractServlet
+    def do_GET request, response
+      response.status = 200
+      response['Content-Type'] = 'text/plain'
+      response.body = "Host: #{request.header['host'].first}"
+    end
+  end
+
+  def start_echo_server(bind_address, port)
+    server = WEBrick::HTTPServer.new(BindAddress: bind_address, Port: port)
+    server.mount('/', HostEchoServer)
+    server
+  end
+
+  describe "requests by IP address" do
+    before(:all) do
+      port = 8080
+      begin
+        @v6server = start_echo_server('::1', port)
+        @v6port = port
+      rescue Errno::EADDRINUSE
+        port += 1
+        retry
+      end
+
+      begin
+        @v4server = start_echo_server('127.0.0.1', port)
+        @v4port = port
+      rescue Errno::EADDRINUSE
+        port += 1
+        retry
+      end
+
+      @server_threads = []
+      @server_threads << Thread.new { @v6server.start }
+      @server_threads << Thread.new { @v4server.start }
+
+      puts "started HTTP servers"
+    end
+
+    after(:all) do
+      puts 'stopping HTTP servers'
+      @v6server.shutdown
+      @v4server.shutdown
+      @server_threads.map(&:join)
+      puts 'stopped'
+    end
+
+    it 'correctly set Host for IPv4 server' do
+      resp = RestClient.get("http://127.0.0.1:#{@v4port}")
+      expect(resp.body).to eq "Host: 127.0.0.1:#{@v4port}"
+    end
+
+    it 'correctly set Host for IPv6 server' do
+      resp = RestClient.get("http://[::1]:#{@v6port}")
+      expect(resp.body).to eq "Host: [::1]:#{@v4port}"
+    end
+  end
 end
diff --git a/spec/unit/request2_spec.rb b/spec/unit/request2_spec.rb
index 71e5d6e..d7f13b3 100644
--- a/spec/unit/request2_spec.rb
+++ b/spec/unit/request2_spec.rb
@@ -32,6 +32,27 @@ describe RestClient::Request do
 
   end
 
+  context "IP addresses in Host header" do
+    it 'passes IPv4 Host header correctly' do
+      stub_request(:get, 'http://127.0.0.1').
+        with(headers: {'Host' => '127.0.0.1'}).
+        to_return(body: 'foo', status: 200)
+
+      expect(RestClient.get('http://127.0.0.1').body).to eq 'foo'
+    end
+
+    # Cannot use webmock to test this because webmock itself handles IPv6
+    # addresses incorrectly. (as of webmock 2.3.2)
+    #
+    # it 'passes IPv6 Host header correctly' do
+    #   stub_request(:get, 'http://[::1]/').
+    #     with(headers: {'Host' => '[::1]'}).
+    #     to_return(body: 'foo', status: 200)
+    #
+    #   expect(RestClient.get('http://[::1]/').body).to eq 'foo'
+    # end
+  end
+
   it "can use a block to process response" do
     response_value = nil
     block = proc do |http_response|